1. Field of the Invention
The present invention relates to an oil seal and more particularly to an oil seal for sealing a clearance between a crankcase and a crankshaft of an internal combustion engine.
2. Description of the Prior Art
An oil seal of this type is known which is incorporated into a bearing for rotatably supporting a crankshaft relative to a crankcase. Since such an oil seal is produced in accordance with a particular specification, a great amount of work and a high cost are needed for the production. In addition, the sealing effect for outer and inner circumferential surfaces of the bearing would be incomplete or unsatisfactory, and the weight of the bearing including the oil seal weight would be unduly increased.
Also, there is provided another type oil seal in which an annular sealing member that is in sliding contact with an outer circumferential surface of the crankshaft is provided in the middle of an annular support member; an outer portion of the support member is made in the form of a sleeve; the sleeve portion is pressingly inserted into an opening of the crankcase that has been subjected to a finish machining work; and the support portion is mounted in place with the end of the sleeve portion being in contact with a thrust bearing plate. However, the oil seal of this type suffers from disadvantages such that it is time-consuming to mount the oil seal and a dead space within the crank chamber would be increased with a degradation in engine efficiency or an increase in a width of the engine.